The present invention relates to compass saws in which flat saw blades are utilized. More particularly, the invention relates to a device for connecting a saw blade to the end of a reciprocating rod of a hand held motor-driven saw.
A connecting mechanism for a saw blade of the foregoing type is disclosed, for example in the U.S. Pat. No. 4,020,555. The connecting mechanism disclosed in the above patent includes a reciprocating shaft having a round cross-section. The saw blade can be easily disengaged from the reciprocating shaft or engaged with it again and thus can be easily replaced by a new one. The problem with this otherwise satisfactory connecting mechanism is that it can not be used for rigidly clamping the saw blade with a very advantageous flat reciprocating rod. The saw blade locked in the connecting device is not mounted there sufficiently rigidly. Therefore an unavoidable clearance or play in a holder for holding the shaft of the saw blade provided for manufacturing reasons causes significant noise during operation of the saw and also increases wear of the shaft of the saw and of the shaft holder provided at the end of the reciprocating shaft. Thus a cut resulting from the use of the known compass saw is not as neat as desired. Furthermore, due to the circular cross-section of the reciprocating rod there are required a coulisse for driving of the reciprocating rod and a precise guide for guiding the saw blade in the feeding direction, which are unnecessary in the case of use of the flat reciprocating rod. The reciprocating shaft or rod and the coulisse are comparatively heavy and their manufacturing is expensive.